Shape memory polymer proppants, methods of making shape memory polymer proppants for application in hydraulic fracturing treatments

ABSTRACT

The present disclosure provides for shape memory proppants, methods for making shape memory proppants, and methods of using shape memory proppants, and the like. The strong expandable proppants of the present disclosure may be used in maintaining fracture openings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication Ser. No. 62/075,407, having the title “SHAPE MEMORY POLYMERPROPPANTS AND METHODS OF MAKING SHAPE MEMORY POLYMER PROPPANTS FORAPPLICATION IN HYDRAULIC FRACTURING TREATMENTS”, filed on Nov. 5, 2014,the disclosure of which is incorporated herein in by reference in itsentirety.

BACKGROUND

Oil and gas production in both conventional and unconventional lowpermeability reservoirs has been heavily relied on hydraulic fracturingtechnology in the last two decades. By utilizing excessive hydraulicpressure to crack the formation rock, artificially generatedpreferential flow paths from the wellbore to the formation couldincrease the contact area between well and reservoir by orders ofmagnitude. Consequently, flow of hydrocarbons can be significantlyfacilitated by highly permeable induced fractures. Proppants are used tokeep the fracture walls apart to create a conductive path to thewellbore after pumping has stopped and the fracturing fluid has leakedoff. Placing the suitable concentration and type of proppant in thefracture is critical to the success of a fracturing treatment. Factorsaffecting the fracture conductivity (a measurement of how a proppedfracture is able to pass the produced fluids over the production life ofthe well) are proppant grain size distribution, proppant-packpermeability, physical properties of the proppant, and long-termdegradation of the proppant. To open and propagate a hydraulic fracture,fluid pressure must overcome the in situ stresses. Proppants areinjected with the fracturing fluid to prevent the potential closure.After the well is put on production, earth stress acts to close theinduced fracture and confine the placed proppants (see FIG. 1). If theproppant strength is inadequate, the closure stress closes the fractureor crushes the proppant, which reduces the conductivity of the proppantpack. Thus, there is a need to produce strong expandable proppants thatovercome current limitations.

SUMMARY

Embodiments of the present disclosure provide for a shape memory polymerproppant, methods of making a shape memory polymer proppant, and methodsof use for a shape memory polymer proppant.

An embodiment of the present disclosure includes a shape memory polymerproppant, wherein the proppant has an activated state and a programmedstate, wherein in the programmed state of the proppant has a programmedstate diameter, wherein in the activated state of the proppant has anactivated state diameter, wherein the activated state diameter is equalto or greater than the programmed state diameter, wherein the proppantin the programmed state will convert to the proppant in the activatedstate when an activation condition is applied to the proppant in theprogrammed state, wherein the activation condition is selected from thegroup consisting of: an activation temperature, a moisture, a light, apH, a magnetic field, an ultrasonic current, electricity current, and acombination thereof. In an embodiment, the polymer material is athermoplastic shape memory polymer or a thermosetting shape memorypolymer. In an embodiment, the shape memory polymer proppant has a coresurrounded by the polymer material.

An embodiment of the present disclosure also includes a method of makinga shape memory polymer proppant, comprising: making a shape memorypolymer proppant, comprising: providing a shape memory polymer proppant,wherein the proppant has a starting state, a programmed state, and anactivated state; changing the shape memory polymer proppant from thestarting state to the programmed state; cooling the shape memory polymerproppant in the programmed state under the first pressure to a coolingtemperature, wherein the shape memory polymer proppant remains in theprogrammed state after cooling; and heating the shape memory polymerproppant in the programmed state to a activation condition, wherein theactivation condition is selected from the group consisting of: anactivation temperature, a moisture, a light, a pH, a magnetic field, anultrasonic current, electricity current, and a combination thereofwherein in the starting state of the proppant has a starting diameter,wherein in the programmed state of the proppant has a programmed statediameter, wherein in the activated state of the proppant has anactivated state diameter, wherein the starting diameter is greater thanthe programmed state diameter, wherein the activated state diameter isequal to or greater than the programmed state diameter, wherein theproppant in the programmed state will convert to the proppant in theactivated state when an activation temperature is applied to theproppant in the programmed state. In an embodiment, the activated statediameter is about 100 μm to 1 mm, and the programmed state diameter isabout 100 μm to 1 mm and the activated state diameter is equal to orgreater than the programmed diameter.

An embodiment of the present disclosure also includes a method ofproviding a shape memory polymer proppant, wherein the proppant has anactivated state and a programmed state, wherein in the activated stateof the proppant has an activated state diameter, wherein in theprogrammed state of the proppant has a programmed state diameter,wherein the activated state diameter is equal to or greater than theprogrammed state diameter, wherein the proppant in the programmed statewill convert to the proppant in the activated state when an activationtemperature is applied to the proppant in the programmed state, whereinthe shape memory polymer proppant is in the programmed state; exposingthe shape memory polymer proppant in the programmed state to theactivation condition, wherein the activation condition is selected fromthe group consisting of: an activation temperature, a moisture, a light,a pH, a magnetic field, an ultrasonic current, electricity current, anda combination thereof; and converting the shape memory polymer proppantin the programmed state to the shape memory polymer in the activatedstate upon exposure to the activation condition, wherein the diameter ofthe shape memory polymer proppant in the activated state has a diameterthat is equal to or greater than the diameter of the shape memorypolymer proppant in the programmed state. In an embodiment, theactivation temperature is about 70 to 180° C. in an embodiment, theactivated state diameter is about 100 μm to 1 mm, the programmed statediameter is about 100 μm to 1 mm, and the activated state diameter isequal to or greater than the programmed state diameter.

Other apparatus, methods, features, and advantages will be or becomeapparent to one with skill in the art upon examination of the followingdrawings and detailed description. It is intended that all suchadditional apparatus, methods, features and advantages be includedwithin this description, be within the scope of the present disclosure,and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be more readilyappreciated upon review of the detailed description of its variousembodiments, described below, when taken in conjunction with theaccompanying drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present disclosure.

FIG. 1 illustrates that in regular proppants, due to the effectivestress increase, hydraulic conductivity of fractures diminishesgradually.

FIG. 2 shows bottomhole net pressure and temperature history during atypical fracturing treatment. Dashed line marks the most likely pointfor the initiation of secondary fractures.

FIG. 3 shows a typical thermomechanical cycle for SMP and SMP foam,figure is after (Li and Nettles 2010).

FIG. 4 demonstrates the manufacturing and programming process of SMPbased proppants.

FIGS. 5A-B show a propped fracture with PMA proppants before (FIG. 5A)and after activation (FIG. 5B).

DISCUSSION

This disclosure is not limited to particular embodiments described, andas such may, of course, vary. The terminology used herein serves thepurpose of describing particular embodiments only, and is not intendedto be limiting, since the scope of the present disclosure will belimited only by the appended claims.

Where a range of values is provided, each intervening value, to thetenth of the unit of the lower limit unless the context clearly dictatesotherwise, between the upper and lower limit of that range and any otherstated or intervening value in that stated range, is encompassed withinthe disclosure. The upper and lower limits of these smaller ranges mayindependently be included in the smaller ranges and are also encompassedwithin the disclosure, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded in the disclosure.

Embodiments of the present disclosure will employ, unless otherwiseindicated, techniques of chemistry, material science, and the like,which are within the skill of the art. Such techniques are explainedfully in the literature.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how toperform the methods and use the structures disclosed and claimed herein.Efforts have been made to ensure accuracy with respect to numbers (e.g.,amounts, temperature, etc.), but some errors and deviations should beaccounted for. Unless indicated otherwise, parts are parts by weight,temperature is in ° C., and pressure is at or near atmospheric. Standardtemperature and pressure are defined as 20° C. and 1 atmosphere.

Before the embodiments of the present disclosure are described indetail, it is to be understood that, unless otherwise indicated, thepresent disclosure is not limited to particular materials, reagents,reaction materials, manufacturing processes, dimensions, frequencyranges, applications, or the like, as such can vary. It is also to beunderstood that the terminology used herein is for purposes ofdescribing particular embodiments only, and is not intended to belimiting. It is also possible in the present disclosure that steps canbe executed in different sequence, where this is logically possible. Itis also possible that the embodiments of the present disclosure can beapplied to additional embodiments involving measurements beyond theexamples described herein, which are not intended to be limiting. It isfurthermore possible that the embodiments of the present disclosure canbe combined or integrated with other measurement techniques beyond theexamples described herein, which are not intended to be limiting.

It should be noted that, as used in the specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a support” includes a plurality of supports. In thisspecification and in the claims that follow, reference will be made to anumber of terms that shall be defined to have the following meaningsunless a contrary intention is apparent.

Discussion

Embodiments of the present disclosure provide for shape memory polymerproppants, methods of making shape memory polymer proppants, methods ofusing shape memory polymer (SMP) proppants, methods for treatinghydraulic fractures using shape memory polymer proppants, and the like.Embodiments of the present disclosure can be used in hydraulicfracturing in oil and gas production, in particular in soft shale gasproduction. Proppants of the present disclosure can be remotelycontrolled by in-situ heating during service conditions without the needto interrupt the production process. Embodiments of the proppants can be“programmed” through mechanical loading and its shape memory effect canbe activated through phase transformation. Active control of theproppants provides engineers the ability to maintain or increase thefracture width during production stages to enhance the hydraulicconductivity of the fracture (well productivity). In other words, thefracture conductivity can be maintained for longer periods of time toenhance oil and gas production.

In an embodiment, the shape memory polymer proppant has a startingstate, a programmed state, and an activated state. A more detaileddescription of the states and conversion of the states are providedbelow in reference to making the shape memory polymer proppant and theExample. In the starting state, the proppant has a starting diameter. Inthe programmed state, the proppant has a program state diameter. In theactivated state, the proppant has an activated state diameter. In anembodiment, the starting state has a diameter greater than theprogrammed state, while the programmed state has a diameter that is lessthan that of the activated state. In an embodiment, the startingdiameter can be about 100 μm to 2 mm. In an embodiment, the programmedstate diameter can be about 100 μm to 1 mm and the activated statediameter can be about 100 μm to 2 mm. In an embodiment, the shape memoryproppant in the starting state is about 20 to 70% larger than the shapememory proppant in the programmed state. In an embodiment, the shapememory polymer proppant in the activated state is about 20 to 50% largerthan the shape memory polymer proppant in the programmed state.

If the shape memory polymer proppant is not spherical in shape, one ormore of the dimensions of the shape memory polymer proppant (e.g.,length, width) will increase in value upon conversion from theprogrammed state to the activated state. Use of the term “diameter”throughout the disclosure is done for convenience and clarity, and oneor more of the dimensions for non-spherical shape memory polymerproppants can correspond to the diameter dimension as used in thedescriptions provided herein.

The shape memory polymer proppant in the programmed state will convertto the shape memory polymer proppant in the activated state when anactivation condition is applied to the shape memory polymer proppant inthe programmed state. In an embodiment, the activation condition can bean activation temperature, a moisture, a light, a pH, a magnetic field,an ultrasonic current, electricity current, and a combination thereof.In an embodiment, the activation temperature can be about 70° C. to 180°C., and is within or above the transition temperature of the polymer.The shape memory polymer proppant in the programmed state can be exposedto the activation temperature in-situ in a well fracture, and as aresult the width of the fracture can be maintained or increased as thediameter of the shape memory polymer proppant increases to that of theshape memory polymer proppant in the activated state.

In an embodiment, the shape memory polymer proppant can be composedentirely of a shape memory polymer material or can have a coating layerof shape memory polymer material around a core. In an embodiment, theshape memory polymer proppant not including a core can have a diameterof about 20 μm to 2 mm or about 100 μm to 2 mm when the shape memorypolymer proppant is in the starting state.

In an embodiment, the core can be a grain of sand, bauxite, ceramics, orother similar particle. In an embodiment, the core can have a diameter(or one or more of dimensions of a non-spherical core) of about 10 to 50microns. In an embodiment, the layer of polymer can have a thickness ofabout 10 to 300 microns when the shape memory polymer proppant is in theactivated state. In an embodiment, the layer of polymer can have athickness of about 5 to 200 microns when the shape memory polymerproppant is in the programmed state. In an embodiment, the polymer is inthe range of 25% to 99% by weight.

In an embodiment, the polymer can be a thermoplastic shape memorypolymer. In an embodiment, the thermoplastic shape memory polymer can beselected for instance from organic thermoplastic polymer in thepolyaryletherketone (PAEK) family (e.g., polyether ether ketone (PEEK)),polypropylene (PP), polystyrene, polyurethane, polynorbornene (e.g.,polynorbornene units that are partially substituted by polyhedraloligosilsesquioxane (POSS)), polyester, polyether, polyethyleneterephthalate (PET), polyethyleneoxide (PEO), poly(1,4-butadiene),poly(vinyl acetate), polyamide-6 (nylon-6), poly(tetrahydrofuran),poly(2-methyl-2-oxazoline), poly(ethylene adipate), MDI/1,4-butanediol,poly(ε-caprolactone), poly vinyl chloride, polyethylene/polyamide blend,and a combination thereof.

In an embodiment, the shape memory polymer can be a thermosetting shapememory polymer. In an embodiment, the thermosetting shape memory polymercan be selected for instance from an organic thermosetting polymer inthe epoxy family (e.g. bisphenol A diglycidyl ether, bisphenol F,epoxidised novolacs, aliphatic epoxy resins, glycyylamin epoxy resin,and the like) or a phenolic family (e.g. Novolacs(formaldehyde/phenol<1), Resoles (formaldehyde/phenol>1),polyhydroxyphenols, and the like). They can also be a blend, acomposite, or an interpenetration network of thermoplastic andthermosetting shape memory polymers.

In an embodiment, the shape memory polymer proppant can be included in amixture including sand, bauxite, and/or ceramic and/or other types ofproppants, where different types can have different dimensions, made ofdifferent polymers, be made of a solid polymer material, be of acore/shell design (e.g., polymer material layer around a core),combinations thereof, and the like.

In an embodiment, the shape memory polymer proppant can be made byheating the shape memory polymer proppant in the starting state to aprogramming temperature under a first pressure to form the shape memorypolymer proppant in the programmed state. Subsequently, the shape memorypolymer proppant in the programmed state is cooled under the firstpressure to a cooling temperature (ambient temperature of about 0 to 40°C.), where the shape memory polymer proppant remains in the programmedstate after cooling. The programming temperature can be about thereservoir temperature. In other words, the programming temperature isgreater than the transition temperature of the polymer, and since themolecular chains of the polymer are flexible, the polymer compressesunder the first pressure. During the cooling process under the firstpressure, the molecular chains of the polymer lock into place, so thatwhen the first pressure is released, the shape memory polymer proppantstays in the programmed state. Heating the shape memory polymer proppantin the programmed state above the transition temperature of the polymerallows the locked molecular chains to release and convert to theactivated state having a greater diameter, or with the same diameter butreleasing stress to support the fracture opening.

In an embodiment, the shape memory polymer proppant can be used tomaintain or widen fractures. Once the shape memory polymer proppant inthe programmed state is positioned in the fracture, the shape memorypolymer proppant can be subject to the activation condition (e.g.,activation temperature). For example, the temperature can increase byinjecting material having a higher temperature and/or through heatingfrom the surrounding material. Upon exposure to the activationtemperature, the shape memory polymer proppant in the programmed stateis converted to the shape memory polymer in the activated state, wherethe diameter of the shape memory polymer proppant in the activated statehas a diameter that is greater than the diameter of the shape memorypolymer proppant in the programmed state. In this way, the shape memorypolymer proppant can be used to maintain or widen fractures.

While embodiments of the present disclosure are described in connectionwith the Example and the corresponding text and figures, there is nointent to limit the disclosure to the embodiments in these descriptions.On the contrary, the intent is to cover all alternatives, modifications,and equivalents included within the spirit and scope of embodiments ofthe present disclosure.

Example 1

Hydraulic Fracturing is recognized as the major approach for economicoil and gas production from low permeability reservoirs like shale ortightsand formations. For fractures to stay open after the fracturingtreatment, some materials, so called proppants, are needed to be pumpedinto the fractures to fill the fracture gap and keeps it wide open underthe compressive overburden weight. In long term productions from thesefractured wells, fractures are prone to closing on proppants as theresult of increase in the rock effective stress due to fluid extraction.One of the grand challenges facing the oil and gas industry is how tomaintaining the proppant functionality in the subsurface wherereplacement of proppants is only possible by refracturing the well. Inthis work, we propose a smart “Expandable Proppants” (EP) to remotelycontrol the force and functionality of injected proppants. The developedsmart EP can respond to in-situ heating during its service conditions,without the need to halt any operation at the well site. This smart EPhas the capability to be programmed through mechanical loading and itsshape memory effect is activated through phase transformation (e.g.,activation condition) by temperature, moisture, light, pH, magneticfield, ultrasonic or electricity current. Active control on EPfunctionality will provide the operators with the ability to maintainthe fracture width during production stages and consequently enhancesthe hydraulic conductivity of the formation. The proposed technology mayreduce the need for refracturing due to fracture closure or proppantembedment in soft formation or highly pressurized deep formations.

Introduction:

Proppant compaction, proppant crushing and proppant embedment have posedvarious challenges for sustainable production from stimulated wellsespecially in soft and deep formations like Haynesville Shales.Experimental measurements show the strong effect of proppant embedmentin reducing fracture conductivity (Lacy et al. 1998, Wen et al. 2007).In general, we can write the stress exerted on proppant bed asσ_(Prop)=σ_(CL)Δσ_(Width) −BHFP,  (1)where σ_(CL), is the closure stress which is essentially determined bythe tectonic stresses and the depth of the fracture, BHFP is theformation fluid pressure. Δσ_(Width) is the stress component induced dueto fracture opening; wider fractures have more tendency to close ontheir surfaces. In general, calculating this stress requires accuratestress analysis to incorporate fractures interactions on each other. Forthe simple case of a single-strand hydraulic fracture with planargeometry the stress component corresponding to crack opening can besimply written asΔσ_(Width)=2Ew _(Prop) /Hπ  (2)

where E is the Young's modulus of the rock, H is the fracture height andw_(prop) is the width of the hydraulic fracture at the end of thetreatment. Here, we focus our attention on improving fracturetransmissibility for a simple case of a double-wing hydraulic fracture.Although, core and outcrop studies on one side and fluid flow behavioron the other side have revealed that most of the unconventionalhydrocarbon resources are located in formations that are naturallyfractured, such as Marcellus Shale (Pommer et al, 2013) and BarnettShale (Patel et al, 2013). The presence of natural fractures in thesereservoirs could be a double-edge sword to hydrocarbon production. Onone hand, open and debonded natural fractures may serve as highlypermeable paths for oil and gas flow, which leads to additionalproductivity. However, hydraulic fractures' interaction with naturalfractures may form complex fracture network (Warpinski and Teufel 1987)and makes treatment design more complicated and stimulation results moreunpredictable; in low permeability formations, transmissibility betweennatural fractures become more significant, and fracture fluid flowingthrough the natural fractures will experience a choke or localizedfracture width reduction (Cipolla et al 2010). The intersection ofhydraulic fractures with natural fractures are always experiencing largestress concentrations which may magnifies later during production lifeof the reservoir (Dahi Taleghani, 2010). Placement of expandingproppants in these chokes would guarantee a sustainable hydrocarbon flowthrough complex fracture network. Hence, expanding proppant may have amore significant impact on production enhancement in the case ofcomplicated fracture networks.

Smart materials have been suggested in the past for a different purposein hydraulic fracturing treatments. Nguyen and Barton (2003) proposedthe use of shape memory alloys (SMA) torsion springs, embedded intodissolvable crusts. The activated SMA springs contact the fracturesurfaces and restrict movement of proppant back out of the fractureduring the production of fluids from the well. In another attempt forreducing proppant production of a hydraulically fractured well,Rodriguez (2009) introduced hair-like spiral SMA based additives intothe fracturing fluid. Smart materials have other applications in oil andgas field including smart downhole devices which are used forcontrolling downhole operations with minimal intervention foractivation/control (Marga and Bhaysar, 2013). These classes of smartdevices may use displacement or flow actuators to control/monitor adownhole oilfield operation. In another example, “smart” proppant isproposed to sense downhole condition in which they can store andtransmit the data to a data retrieval device on the surface or in thedrill string (Soliman et al. 2009). In general, SMAs are very expensiveand considerably heavy to be used in large volume as a proppant. Hence,we prefer to explore the possibility of utilizing shape memory polymers(SMP) for this purpose.

FIG. 2 shows a typical recording of the bottomhole pressure andtemperature measurement during fracture stimulation. Fluid and proppantshave been pumped for a period of time, and the termination of thepumping period is marked by a dashed line and followed by an extendedperiod of shut-in that lasts much longer than the pumping time. Ofparticular interest here is that minimum temperature and minimumfracturing fluid pressure occurs almost simultaneously within a shortperiod of time after pump shut-in. The proposed proppant should not onlysustain the high reservoir temperature (high T_(g)) to avoid largeplastic deformation but also being slightly below the reservoirtemperature to release their stored stress. It is notable that therelease stress should be large enough to open the crack but not toolarge to crush the formation rock, hence we are looking for stressrelease ranging from 10-50 MPa, which is not a reachable range with mostexisting shape memory polymers. Additionally, smart proppants can bepumped simultaneously with the regular proppants in the form of batchesto locally widen the fractures in patches like a jack.

In this example, we introduce a new generation of SMP based smartproppants, which may actively control and maintain the applied forces onthe fracture surfaces; since more expanded proppants would be engagedwith the fracture walls, these proppants can simultaneously act as anactive filter for preventing sand/proppant production from the well.Applicability, production and functionality of Shape Memory Polymer(SMP) based proppants to enhance fracture conductivity is disclosed inthis work.

Shape Memory Based Smart Materials:

Shape memory polymers (SMPs) are capable of storing a prescribed shapeindefinitely and recover them by specific external trigger, e.g. heat.SMPs have potential to be deployed in various engineering structures anddevices. In the case of Shape Memory materials, the programming andshape recovery process can be well described by the thermomechanical(TM) cycle shown in FIG. 3 for a pure amorphous SMP and SMP basedsyntactic foam. In general, four steps are included in this cycle: (1)High temperature loading: the temperature is elevated to above thetransition temperature, i.e. T_(r), where the mobility in the SMPmolecular network is surged. The SMP molecular chains are flexible inthis stage and they can cope with the applied external traction field.(2) Cooling: The SMP is cooled down to below T_(r) while the externaltraction field is maintained. In this step, the deformed molecularnetwork retains the induced shape in step 1. (3) Low temperatureunloading: The traction is then removed which result in elasticunloading of the SMP and completing the programming process, and (4)Recovery: During the shape recovery stage the temperature is increasedbeyond the transition temperature where the locked molecular chains areable to restore their original configuration and in this step, the SMPreleases its memory (see Li and Nettles 2010; Li and Uppu 2010; Hager etal, 2015). Considering the high temperature of oil and gas reservoirs,both thermoplastic and thermoset SMPs can be used for this purpose.Programming can also be conducted at temperatures below the transitiontemperature such as cold compression programming for amorphousthermosetting SMPs (Li and Xu 2011) or cold-drawing programming forsemi-crystalline thermoplastic SMPs (Li and Shojaei 2012).Theoretically, SMP recovers once the temperature enters the glasstransition (T_(g)) region (usually, T_(g) is the center of this region).If recovery occurs at the lower temperature side of the T_(g) region,the recovery rate is low, but SMP proppant will ultimately recover tothe final shape at reasonable time scale before production drop in thewellbore. It is notable that, by so-called cold programming (Li and Xu2011), programming may not need the typical heating and cooling process.

There are SMP developed with polyether ether ketone (PEEK) which is asemicrystalline thermoplastic polymer with transition temperature higherthan 150° C. and good mechanical strength and Young's modulus. All theseproperties make this material desirable for the application in hydraulicfracturing treatments (Shi et al. 2013).

Smart Proppant Design and Applications:

Due to the high cost of other smart materials, SMP would be a morepractical option for manufacturing smart proppants. SMPs can be used asproppants in two forms. In the first form, SMP particles can be mixedwith the regular proppants (for instance sand particles) and then isbeing pumped into the fracture. In the second case, the conventionalsand based proppants are coated with SMP material and then the coatingis programmed under higher temperature in which hydraulic forces areused to deform the SMP at elevated temperature. By maintaining anapplied pressure during cooling cycle, the SMP coating is programmed.FIG. 4 demonstrates the manufacturing and programming process of SMPbased proppants. In the case of SMP based proppants, the conventionalsand based proppants are coated with an SMP material (stages 1 and 2 inFIG. 4). The coated proppant then undergoes programming cycle (stage 3in FIG. 4) which is (a) heating process until T>T_(g), (b) applyinghydrostatic pressure P, (c) while maintaining the pressure thetemperature is decreased to T<T_(g). The programmed proppant (stage 4 inFIG. 4) is now ready to be deployed in fractured volume. Upon heatingthe programmed proppants, the SMP coating is activated and recovers itsoriginal shape. During the process of the shape recovery, releasedpressure will act on the fracture surfaces to keep the fracture open oreven widen the fracture.

The smart proppant in this case is activated via heating sources fromthe wellbore environment and it can effectively widen the gaps withinthe fractures (FIGS. 5A-B). These expanding proppants may also be usedin the last batch of pumped slurry to retain the proppants inside thefracture. Proppant flow-back may occur in very low-permeable formations;the expanded proppants would prevent the proppants from flowing backinto the wellbore.

A new generation of proppants is proposed in this disclosure to preventor at least postpone hydraulic fractures closure to enhance theproduction from unconventional hydrocarbon reservoirs. Currently,hydraulic fracturing is a main venue for economic oil and gas productionfrom low permeability shale reservoirs but production usually diminishesafter a short time after well stimulation. Increase in rock closurestress due to fluid extraction may crash proppant or cause proppantembedment in the long-term. The proposed smart proppants provide thecapability to in-situ maintain/control proppants' functionality. Thedeveloped smart EP can respond to in-situ heating during its serviceconditions, without the need for refracturing the well. This smart EPhas the capability to be programmed through mechanical loading, itsshape memory effect can then be activated through phase transformation.Considering the fact that the proposed smart proppants can bemanufactured in different sizes without any practical limitation, anygiven proppant size distribution to obtain a certain proppant bedpermeability can be achieved using this technology.

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It should be noted that ratios, concentrations, amounts, and othernumerical data may be expressed herein in a range format. It is to beunderstood that such a range format is used for convenience and brevity,and thus, should be interpreted in a flexible manner to include not onlythe numerical values explicitly recited as the limits of the range, butalso to include all the individual numerical values or sub-rangesencompassed within that range as if each numerical value and sub-rangeis explicitly recited. To illustrate, a concentration range of “about0.1% to about 5%” should be interpreted to include not only theexplicitly recited concentration of about 0.1 wt % to about 5 wt %, butalso include individual concentrations (e.g., 1%, 2%, 3%, and 4%) andthe sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within theindicated range. In an embodiment, the term “about” can includetraditional rounding according to significant figures of the numericalvalue. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ toabout ‘y’”.

While only a few embodiments of the present disclosure have been shownand described herein, it will become apparent to those skilled in theart that various modifications and changes can be made in the presentdisclosure without departing from the spirit and scope of the presentdisclosure. All such modification and changes coming within the scope ofthe appended claims are intended to be carried out thereby.

We claim at least the following:
 1. A method, comprising: providing ashape memory polymer proppant to a fracture in a well, wherein the shapememory polymer proppant is composed entirely of a shape memory polymermaterial where the shape memory polymer material is a thermoplasticshape memory polymer, a thermosetting shape memory polymer, or acombination thereof, wherein the proppant has an activated state and aprogrammed state, wherein in the activated state of the proppant has anactivated state diameter, wherein in the programmed state of theproppant has a programmed state diameter, wherein the activated statediameter is equal to or greater than the programmed state diameter,wherein the proppant in the programmed state will convert to theproppant in the activated state when an activation temperature isapplied to the proppant in the programmed state, wherein the shapememory polymer proppant is in the programmed state; exposing the shapememory polymer proppant in the programmed state to the activationcondition in the fracture, wherein the activation condition is anactivation temperature; and converting the shape memory polymer proppantin the programmed state to the shape memory polymer in the activatedstate upon exposure to the activation condition in the fracture, whereinthe diameter of the shape memory polymer proppant in the activated statehas a diameter that is equal to or greater than the diameter of theshape memory polymer proppant in the programmed state, wherein theactivated state diameter is about 100 μm to 1 mm, wherein the programmedstate diameter is about 100 μm to 1 mm, and wherein the activated statediameter is equal to or greater than the programmed state diameter. 2.The method of claim 1, wherein the thermosetting shape memory polymer isselected from the group consisting of: an epoxy family and a phenolicfamily.
 3. A method, comprising: providing a shape memory polymerproppant to a fracture in a well, wherein the proppant has an activatedstate and a programmed state, wherein in the activated state of theproppant has an activated state diameter, wherein in the programmedstate of the proppant has a programmed state diameter, wherein theactivated state diameter is equal to or greater than the programmedstate diameter, wherein the proppant in the programmed state willconvert to the proppant in the activated state when an activationtemperature is applied to the proppant in the programmed state, whereinthe shape memory polymer proppant is in the programmed state, whereinthe shape memory polymer proppant consists of a polymer material,wherein the polymer material is a thermosetting shape memory polymer isselected from the group consisting of: an epoxy family and a phenolicfamily; exposing the shape memory polymer proppant in the programmedstate to the activation condition in the fracture, wherein theactivation condition is selected from the group consisting of: anactivation temperature, a moisture, a light, a pH, a magnetic field, anultrasonic current, electricity current, and a combination thereof; andconverting the shape memory polymer proppant in the programmed state tothe shape memory polymer in the activated state upon exposure to theactivation condition in the fracture, wherein the diameter of the shapememory polymer proppant in the activated state has a diameter that isequal to or greater than the diameter of the shape memory polymerproppant in the programmed state.